With the development of science and technology and the progress of society, the country has been promoting the development of high technology. In the technical field of the bridge welding, there has always been a difficult technical problem that a steel reinforcing cage needs to be welded in the general and normal bridge welding constructions, and the welding of the steel reinforcing cage requires the circumferential outer surface and the interior to be welded at the same time, but the ordinary welding machines only weld outside steel reinforcing cages, and the internal welding opening can not be welded. Moreover, it is not easy to adjust the welding diameter of the steel reinforcing cage and not convenient to weld steel reinforcing cages with various diameters, however this device effectively solves the problem.